“It is common knowledge that censorship does exist in China and that the Chinese government has been monitoring communications in and out of the country for many years,” he said.

He recalled that in April 2006, Skype admitted that TOM Online “operated a text filter that blocked certain words in chat messages” and unsuitable messages were to be “discarded and not displayed or transmitted anywhere.”

“It was our understanding that it was not TOM’s protocol to upload and store chat messages with certain keywords, and we are now inquiring with TOM to find out why the protocol changed,” he said.

“We are currently addressing the wider issue of the uploading and storage of certain messages with TOM,” Silverman said, stressing that the millions of people around the world using standard Skype software were unaffected.